Motor vehicle control device with regulation and/or limitation of driving speed

ABSTRACT

A vehicle engine control apparatus has a driver-operated engine operation preset control element and a speed regulation stage and/or limiting stage for regulating or limiting, respectively, the speed of travel using an engine-power-related nominal preset signal and emitting an engine-power-related speed regulation or speed limiting control signal. A torque characteristic stage emits an engine-torque related nominal preset signal as a function of the operation of the engine operation preset control element and of engine rotation speed information. This nominal preset signal is supplied to an engine/power characteristic stage which is provided on the input side of the speed regulation or limiting stage and determines the engine-power-related nominal preset signal from this as a function of the engine rotation speed. The engine-power-related speed regulation or speed limiting control signal is transformed to an engine-torque-related control signal by means of a power/torque characteristic stage on the output side.

This application claims the priority of PCT International ApplicationNo. PCT/EP99/02737, filed Apr. 23, 1999 and German patent document 19820 830.8, filed May 9, 1998, the disclosure of which is expresslyincorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a vehicle engine control device having adriver-operated engine operation preset control element and a speedregulation and/or limitation stage which regulates or limits the vehicletravelling speed, using an engine-power-related nominal preset signaland emitting an engine-power-related control signal (DE 44 39 424 C1).

Various versions of such vehicle engine control devices are known. Theengine operation preset control element is used by the driver toinfluence engine operation in a desired manner; that is, to demand adesired engine operating state. Traditionally, this control element isan accelerator pedal, which can be deflected by the driver and whosedeflection represents the engine operating state desired by the driver.In the most widely used, conventional system type, as is traditionallyused in motor vehicle internal combustion engines having a throttlevalve, the accelerator pedal deflection is interpreted as demanding acorresponding setting for the throttle valve position, and thus as anengine-power-related setting signal, for example in the form of theclassical mechanical coupling between the accelerator pedal and thethrottle valve. Speed regulation units and speed limiting units, such asthose which have been introduced by the Applicant under the designationsTempomat™ and Speedtronic™, operate on this basis at the throttle valveposition preset level. They are thus related to engine power, in thatthey are supplied with the accelerator pedal position information as anengine-power-related nominal preset signal and they emit anengine-power-related control signal for regulating the throttle valveposition and, possibly, other engine power parameters, in particular thefuel injection parameters, in such a way that the speed of travel isregulated or limited at a desired nominal value. One example of such anapparatus is disclosed in German Patent Document DE 37 10 891 A1.Another speed regulation system of this conventional type, which isparticularly suitable for Otto-cycle or diesel engines with injection,is described in German Patent Document DE 44 39 424 C1, which hasalready been cited above.

This conventional regulation and/or limiting of the speed of travel atthe throttle valve position level, and thus at the engine power level,has a self-stabilizing effect. This is because, as the rotation speedincreases, the amount of combustion air with which the cylinder isfilled is reduced, so that the engine torque decreases and, inconsequence, the power is reduced. When the rotation speed decreases, onthe other hand, the cylinder filling, and thus the engine torque,increase, and in consequence the engine power rises. With this response,the engine thus automatically acts in the same sense for regulation orlimiting of the speed of travel in the sense of negative feedback, inthat the engine torque setting is reduced when the vehicle goes toofast, while the engine torque is increased when the vehicle goes tooslow.

Since the speed of travel can be linked to the engine rotation speed viathe circumference of the vehicle wheels and via the axle andtransmission step-up ratios, regulation and limiting systems for thevehicle speed are, in the final analysis, rotation speed regulationsystems and limiting systems, respectively. In consequence, presetting adesired nominal or limiting speed is equivalent to presetting acorresponding, constant engine rotation speed, which means that in theclassical throttle-valve-position-related systems, the throttle valveposition, and thus the engine torque as a dependent variable, are set inproportion to the speed control error, with the entire adjustment rangebeing available. The clear association between the control signalemitted from the regulation or limiting system for the desired enginepower is thus provided.

Recently, vehicle engine control devices have become of increasinginterest which operate at the engine torque level, that is to say with atorque structure. This means that the setting of the engine operationpreset control element, for example an accelerator pedal, is assessed asa driver demand for a specific engine torque, and not on for a specificthrottle valve position or engine power. In these engine controllers,which have recently become of increasing interest, based on an enginetorque preset, an appropriate throttle valve position or an equivalentengine power parameter for the driver's demand, as expressed by him byoperation of the engine operation preset control element, is determinedonly at the end of the engine control action chain, generally on thebasis of a suitable engine model. The operation of the engine operationpreset control element thus no longer has any direct effect on thethrottle valve position, which term, in the following text, also refersto any other, equivalent engine power parameter, particularly in thecase of an engine without a throttle valve.

This has exacerbating effects for systems where the speed of travel isregulated and/or limited automatically, because a constant torque presetcan be associated with arbitrary engine rotation speeds over wideranges. If, now, the engine is intended to maintain a specific rotationspeed for the present torque preset, for example because the resistanceto movement is not forcing any reduction in speed, then this can lead tothe vehicle speed being in an unacceptably wide range for precise speedregulation. Furthermore, a constant torque preset means that, in theevent of an increase in rotation speed which would result in the torquebeing reduced, the torque reduction is compensated for by continuousopening of the throttle valve in order to maintain the torque preset.Even though the vehicle speed is increasing, the throttle valve is thusopened further, so that, in the speed regulation system, the controlerror is first of all increased; that is, there is a positive-feedbackeffect in the positive direction. Analogously, there is apositive-feedback effect in the negative direction when the rotationspeed decreases, in which case the torque would be reduced. But this iscompensated for by continuous closure of the throttle valve in order tomaintain the torque preset; that is, the throttle valve is closedfurther even through the vehicle is slowing down, so that the controlerror of the speed regulation system is once again increased. Thus,without any further actions, the engine in such engine control systemsbased on torque automatically acts in the opposite sense to conventionalregulation and/or limiting of the speed of travel on a throttle valveposition or engine power basis, thus not ensuring stable speedregulation or limiting.

In a motor vehicle described in European Patent Document EP 0 299 235 A2and having a speed regulation device, operation of the accelerator pedalis interpreted as presetting a desired speed of travel.

One object of the invention is to provide a vehicle engine controlapparatus of the type mentioned initially which operates at the torquelevel, and also allows satisfactory regulation and/or limitation of thespeed of travel.

This and other objects and advantages are achieved by the controlarrangement according to the invention, in which a torque characteristicstage is provided, which emits an engine-torque-related nominal presetsignal as a function of the operation of the engine operation presetcontrol element, normally an accelerator pedal. The engine operatingstate demand expressed by the driver on the control element is in thisway interpreted as a torque demand; that is, the engine control systemoperates on a torque basis, and forms a torque structure. A conventionalspeed regulation or speed limiting stage operates at the throttle valveposition level (that is, the engine power level).

Characteristically, the input side of the speed regulation or speedlimiting stage has an associated torque/power characteristic stage,which transforms the engine-torque-related nominal preset signal,produced by the torque characteristic stage from the engine operationpreset control element signal, into an appropriate nominal preset signalwhich is related to the engine power, and is thus related to thethrottle valve position. The latter signal can then be processed in aconventional manner by the subsequent speed regulation stage or speedlimiting stage, which operates at the throttle valve position level, andthus at the engine power level. In a corresponding way, the output sideof the speed regulation or speed limiting stage has an associatedpower/torque characteristic stage, which corresponds to the inverse ofthe torque/power characteristic stage on the input side. Thepower/torque characteristic stage is used to transform the controlsignal emitted from the speed regulation or speed limiting stage at thethrottle valve position level (that is, the engine power level) into acontrol signal at the engine torque level.

Thus, overall, a speed regulation and/or speed limiting stage whichoperates in a conventional manner at the engine power level is embeddedat a suitable point in the torque structure of an engine control systemoperating at the engine torque level. Although embedding this behind thetorque characteristic stage involves the use of the torque/powercharacteristic stage and the power/torque characteristic stage, thisallows the destabilizing characteristics of the downstream enginecontrol action chain to be taken into account correctively in itscharacteristics. Furthermore, in consequence, the action chain of thespeed regulation or speed limiting stage remains decoupled from theapplication of an accelerator pedal characteristic which determines thedriving characteristics, so that any change in these drivingcharacteristics does not affect any previous application of the speedregulation or speed limiting stage and, in consequence, interactiverelationships are avoided.

It is furthermore advantageous that the extremely well-proven,conventional regulator and limiter structures, which operate at theengine power level, can be transferred unchanged to the speed regulationstage and the speed limiting stage, irrespective of the type of aircontrol used by the engine, and irrespective of what variable is used asthe regulated variable when the engine torque does not represent thesuitable regulated variable. Furthermore, the torque structure of theengine control system can be designed and optimized entirely on thebasis of engine factors, without the speed regulation and limitingplacing any limitations on this. The path gain of the control path forregulating or limiting the speed is the same as that at the throttlevalve position level, which is higher than at the torque level,irrespective of the type of regulator.

One embodiment of the invention includes not only speed regulation butalso speed limiting in parallel therewith; and maximum and minimumselection units are provided in a suitable way on the output side of thespeed regulation stage and the speed limiting stage, respectively. Themaximum selection unit allows the speed regulation to be overwritten bycorresponding driver operation of the engine operation preset controlelement, while the minimum selection unit ensures that a selectedlimiting speed is not overshot.

Another embodiment of the invention also includes an electricaltransmission control which advantageously operates, when the speedregulation or speed limiting is active, on the basis of the enginetorque setting produced at the torque level on the output side of thespeed regulation or speed limiting stage. For this purpose the enginetorque setting is transformed by a characteristic stage which is theinverse of the torque characteristic stage, to a transmission controlpreset signal at the level of the operating variable of the engineoperation preset control element. When speed regulation and speedlimiting are inactive, the transmission control preset signal issupplied in a conventional manner directly from the operating signal forthis control element (that is, always at the engine power level) inevery case.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The single FIGURE shows a block diagram of that part of a vehicle enginecontrol apparatus according to the invention, which has speed regulationand speed limiting functionality.

DETAILED DESCRIPTION OF THE DRAWINGS

The vehicle engine control apparatus whose section of interest is shownin the FIGURE is of the type based on a torque preset, from which anengine-power-related control signal, such as a throttle valve nominalposition signal, is calculated only at the end of the engine controlaction chain. The engine operation preset, which can be preset by thedriver, is thus an engine torque preset, with an accelerator pedal(which is not shown) being used as normal as the engine operation presetcontrol element.

Such an engine control system at the torque level has certainadvantages, for example when used in conjunction with wheel-slittraction control systems and electronic driving stability systems, suchas the system with the abbreviation ESP™ introduced by the Applicant. Inorder to transform the accelerator pedal position to the torque level,it is detected by an accelerator pedal position sensor (not shown) whoseoutput signal is supplied as an accelerator pedal position signal 1 to afirst input of a torque characteristic stage 2, whose second input 3receives an information signal relating to the engine rotation speed N.The torque characteristic stage 2 uses these two input variables and acharacteristic stored therein (and having a progressive profile, whichis designed for the driving characteristics and good metering capabilityfor the engine torque) to calculate the associated torque preset; (thatis, the engine torque currently demanded by the driver via theaccelerator pedal), and emits an appropriate engine torque preset signal(nominal preset signal) 4.

The vehicle engine control apparatus includes a conventional speedregulation stage 5 (that is, a Tempomat™, and a conventional speedlimiting stage 6, such as a Speedtronic™, in parallel with it). Thespeed regulation stage 5 comprises the actual regulator unit 7, aprogression factor stage 8 following it on the output side, and adegression factor stage 9 connected upstream on the input side. Thespeed limiting state 6 analogously comprises the actual limitingregulating unit 10, with a progression factor stage 11 connecteddownstream on the output side, and a degression factor stage 12connected upstream on the input side. The two progression factor stages8, 11 of the speed regulation and speed limiting stages 5 and 6 arepreferably identical, as the two degression factor stages 9, 12 are alsoanalogous to them. The respective progression factor stage 8, 11 is usedto multiply the regulator output signal supplied on the input side by asuitable factor, which is determined from a stored characteristic with aprogressive profile as a function of the regulator output signal. Thisis used for appropriate amplification of the regulator signal. Theprogressive profile corresponds to the profile of the engine powerrequirement characteristic. The reason for using the progression factorstage 8, 11 is that this engine power requirement characteristic istypically noticeably non-linear, while the behaviour of the upstreamregulator units is essentially linear. The respective degression factorstage 9, 12 is used to invert this process on the input side, that is tosay the input signal supplied to the associated regulator unit 7, 10 ismultiplied by a degressive factor which corresponds to inversion of thefactor of the progression factor stage 8, 11 on the output side, and forwhich purpose inverse characteristics are stored in a correspondingmanner in the degression factor stages 9, 12.

The speed regulation stage 5 and the speed limiting stage 6 operate in acorresponding manner to the conventional system design at the enginepower level, that is to say the throttle valve position level, and arethus not suitable for direct connection to the engine torque presetsignal 4, which is at the torque level, for the reasons mentioned above.To overcome this, a torque/power characteristic stage 13 a, 13 b isrespectively provided upstream of the speed regulation stage 5 and ofthe speed limiting stage 6, these torque/power characteristic stages 13a, 13 b being identical to one another and being supplied via a firstinput with the torque preset signal 4, while they receive the enginerotation speed information N via a second input. The respectivetorque/power characteristic stage 13 a, 13 b now uses a suitably storedcharacteristic to determine an engine-power-related output signal(nominal preset signal) 14 a, 14 b as a function of the instantaneoustorque demand 4 and the engine rotation speed N. The torque/powercharacteristic stage 13 a, 13 b in consequence ensures that the nominalpreset signal 4, which is at the torque level, is converted back to theaccelerator pedal position level, or engine power level.

To a first approximation, the engine/power characteristic stored in itfor this purpose may be regarded as the inverse of the characteristicwhich is stored in the torque characteristic stage 2. In an improvedsystem design, the torque/power characteristic stage 13 a, 13 b alsosuitably takes account of instabilities in the downstream engine controlstructure, so that the correspondingly preset characteristic does not ingeneral correspond exactly to the inverse characteristic of the torquecharacteristic stage 2. Such regulation instabilities are produced inparticular by the interaction of the progressively running,rotation-speed-weighted characteristic for conversion from theaccelerator pedal position level to the engine torque level using anair-mass nominal value characteristic, on the basis of which theappropriate air mass nominal value is calculated for the determinedtorque demand. These instabilities can be overcome by suitably modifieddata assignments for the (stability) characteristic stored in thepower/torque characteristic stage 16.

The output signal 14 a, 14 b from the torque/power characteristic stage13 a, 13 b provides a signal at the engine power or throttle valveposition level which represents the present engine operation demand bythe driver at this level, as is conventionally the case with theaccelerator pedal position signal, so that this output signal 14 a, 14 bforms an input signal which can be used for the speed regulation stage 5and the speed limiting stage 6. Since the torque/power characteristicstage 13 a, 13 b and the degression factor stage 9, 12 upstream of thespeed regulator unit 7 on the one hand and upstream of the limitingregulator unit 10 on the other hand are respectively identical, it issufficient, as an alternative to the illustrated double use, to use ineach case only one torque/power characteristic stage and/or digressionfactor stage 9, 12 jointly for the speed regulator unit 7 and thelimiting regulator unit 10.

The regulator output signal (speed regulation control signal) 15 emittedby the speed regulation stage 5 can now once again be transformed fromthe engine power level to the torque level. For this purpose apower/torque characteristic stage 16 receives the regulator outputsignal 15 as a first input, and the engine rotation speed information asa second input. The power/torque characteristic stage 16 uses theregulator output signal 15 supplied to it to produce the associatedtorque-speed regulation control signal 17, weighted as a function of theengine rotation speed, on the basis of a suitable, stored stabilitycharacteristic; this control signal 17 represents the influence of thespeed regulation stage 5 on the engine torque control. Thecharacteristic stored in the power/torque characteristic stage 16corresponds to the inverse of the characteristic stored in thetorque/power characteristic stage 13 a, 13 b on the input side.

In the same way, a further power/torque characteristic stage 18, whichis identical to the already mentioned power/torque characteristic stage16, is used on the output side of the limiting stage 6 to transform thespeed limiting control signal 19 (emitted from the latter) from theengine power level and weighted as a function of the engine rotationspeed, to a torque/speed limiting control signal 20 at the torque level.

The torque/speed regulation control signal 17 is supplied to a firstinput of a maximum selection stage 21, which receives the torque presetsignal 4 via a second input and emits the larger of the two signals onthe output side. The maximum evaluation stage 21 thus ensures that thedriver can use the accelerator pedal to override the influence of thespeed regulation, that is to say he can accelerate the vehicle beyondthe regulation influence when he operates the accelerator pedalappropriately hard. The output signal 22 emitted from the maximumselection stage 21 is supplied to a first input of a minimum selectionstage 23, which receives the torque/speed limiting control signal 20 ata second input and passes on the smaller of the two input signals as theengine torque control signal 24. The minimum selection stage 23 ensuresthat the engine torque setting cannot be any higher than that allowed bythe speed limiting stage 6. The engine torque control signal 24 is thensupplied to a downstream engine control apparatus (not shown), which isof no further interest here, but includes, in particular, an enginemodel to which the engine torque control signal 24 is applied, in orderto calculate the air mass nominal value for the filling of the enginecylinders and the various fuel injection parameters and, accordingly, toset the corresponding operating parameters for the engine.

The vehicle engine control device has an associated electronictransmission controller (not shown), to which an associated transmissionnominal setting signal (nominal value signal) 25 is supplied from acontrollable switch 26, which can be switched between two switch inputs.To one such input the accelerator pedal position signal 1 is applied,and to the other the output signal 27 from a transmission controlcharacteristic stage 28 is applied.

The transmission control characteristic stage 28 is used to transformthe engine torque control signal 24, which is at the torque level, intothe output signal 27 at the accelerator pedal level, for transmissioncontrol. To this end, apart from the engine torque control signal 25,the transmission control characteristic stage 28 receives the enginerotation speed information via a second input and uses the engine torquecontrol signal 24 to determine, weighted by the rotation speed, thetransmission control output signal 27 on the basis of a characteristicwhich is the inverse of that in the torque characteristic stage 2 and isthus used to map a speed regulator signal from the torque level to theaccelerator pedal level, for transmission control.

If neither the speed regulation stage 5 nor the speed limiting stage 6is active, the switch 26 passes on the accelerator pedal position signal1 as the transmission nominal setting signal 25. If either the speedregulation stage 5 or the speed limiting stage 6 is active, the switch26 is switched by an OR stage 29 to its other position, so that thetransmission nominal setting signal 25 is formed by the output signal 27from the transmission control characteristic stage 28. In this manner,the transmission control can react properly to the engine controlmeasures from the speed regulation stage 5 and/or from the speedlimiting stage 6.

In order to control the switch, the OR stage 29 is supplied via a firstinput from the maximum selection stage 21 with an information signal 30defining whether the maximum selection stage 21 is at that time activelypassing on the signal 17 produced by the speed regulation. At the sametime, via a second input, the OR stage 29 receives an information signal31 from the minimum selection stage 23 defining whether the latter is atthat time actively passing on the signal 20 produced by the speedlimiting.

As shown, the speed regulation stage 5 and the speed limiting stage 6are arranged behind the torque characteristic stage 2 in the controlsignal direction. Despite the resulting necessity for the torque/powercharacteristic stage 13 a, 13 b, this arrangement has major advantagesover a feasible, direct link between the speed regulation stage 5 and/orthe speed limiting stage 6 and the accelerator pedal position signal 1.This is because, in the latter case, it might not be possible to correctfor the destabilizing influences of the subsequent engine control actionchain, which has been mentioned above. By virtue of the torque/power andpower/torque characteristic stages 13 a, 13 b , 16, 18, the paths ofaction of the two regulating units 7, 10 are decoupled from theapplication of the accelerator pedal characteristic, which is used todetermine the driving characteristics. In consequence, any change in theaccelerator pedal characteristic or in the driving characteristics hasno effect on any previous application of the regulating units 7, 10, andinteractive relationships are thus avoided.

On the other hand, the change to the data assignment (which is feasibleas an alternative to the described construction of the engine controlapparatus) of all the characteristics which are responsible for thepositive-feedback response, rather than a negative-feedback response,for torque presetting rather than power presetting, as described above,is not worthwhile. Although this would allow the stabilitycharacteristics to be achieved at the throttle valve position level, andwould allow the regulator units to operate virtually on the basis of thethrottle valve position, it would also make it impossible to exploit theadvantages of the torque structure for improving the driving dynamics.

In operating phases without active speed regulation and speed limiting,the engine control effect path acts in such a way that the driver'storque demand 4. is obtained via the torque characteristic stage 2 fromthe accelerator pedal position set by the driver, and is passed on viathe maximum selection stage 21 and the minimum selection stage 23 as theengine torque control signal 24. It is then used to determine, interalia, the associated throttle valve position for the required air massflow via the downstream functional blocks and characteristics (notshown), and to set the corresponding engine torque. The air mass nominalvalue characteristic already mentioned above has significant influencein this downstream engine control structure, and uses the torque demand(as represented by the engine torque control signal 24) to generate anappropriate air mass nominal value.

When at least one of the speed regulation and speed limiting stage isactive, the driver's torque demand 4 is transformed back via thetorque/power characteristic stage 13 a, 13 b to the accelerator pedalposition level. As mentioned previously, instabilities in the downstreamcontrol structure are counteracted, after which the resulting signal isconverted via the degression factor stage 9, 12, and is supplied to theassociated regulator unit 7, 10 as the initialization value for theaccelerator pedal position. The regulator unit 7, 10 produces an outputsignal as a function of the speed control error or the error between theactual speed and the predetermined, limiting speed; matching to thepower characteristic of the vehicle is then carried out in the forwarddirection, using this output signal and on the basis of the progressionfactor stage 8, 11. The subsequent power/torque characteristic stage 16,18 transforms the setting determined by the associated regulator unit 7,10 to the torque level taking account of the engine rotation speed and,in the process, creates self-stabilizing operating conditions, in thesame way as those which occur with the conventional speed regulation andlimiting based on a throttle valve position preset.

As is evident from the example explained above, the vehicle enginecontrol apparatus according to the invention has a number of significantadvantages. Firstly, the extremely well-proven structure of conventionalspeed regulation and speed limiting devices which operate at thethrottle valve position level (that is, the engine power), and areequally well suited for diesel engines and Otto-cycle engines, can betransferred unchanged. It is in this case irrelevant whether the engineis a naturally aspirated engine with a clear association between theengine power and the throttle valve opening, a supercharged engine, inwhich the power may increase despite the throttle valve opening beingdecreased, an Otto-cycle engine with direct injection, in which thethrottle valve is fully open over wide operating ranges, or an enginewith any other type of air control.

The engine control structure according to the invention can even be usedwhen the engine torque is not a suitable controlled variable, and thelatter is thus formed by another variable. The torque structure forengine control may be designed and optimized entirely on the basis ofengine aspects, without being impeded by structural requirements forspeed regulation or limiting. All the advantages of such a torquestructure can be utilized since there is no need to simulate thestability, corresponding to the throttle valve position level, in themain control action chain. The working level of accelerator pedal andregulator presets is distinguished by exact identification of which ofthe nominal value presets is currently acting. Furthermore, changes fromone action path to the other are clear, and precise regulatorinitialization is possible. The path gain of the control pathcorresponds to that at the throttle valve position level and is higherthan at the torque level, to be precise irrespective of what type ofregulator is used, for example a P, PI, PID or PDT1 regulator.

A further advantage of the apparatus according to the invention is thatit allows the production of a nominal setting signal for transmissioncontrol at the accelerator pedal position level even when the speedregulation or limiting is active (that is, in a virtually identical wayto the accelerator pedal position signal). Thus, the gear-selectioncharacteristic of the transmission is unchanged despite torque-basedengine control when the speed regulation or limiting is activated.Furthermore, all the engine adaptation processes, such as those relatingto air pressure, temperature and friction conditions, are taken intoaccount equally via the accelerator pedal for vehicle management in theactivation of the speed regulation and limiting, although this is notpossible to this extent by linking the speed regulation stage and/or thespeed limiting stage to any point in the engine control/torque structureother than that according to the invention since, then, theseadaptations could be entirely or partially ineffective.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

What is claimed is:
 1. Vehicle engine control device for a vehiclehaving a driver-operated engine operation preset control element, saiddevice comprising: a torque characteristic stage which emits anengine-torque-related nominal preset signal as a function of operationof the engine operation preset control element and of engine rotationspeed information; a torque/power characteristic stage which uses theengine-torque-related nominal preset signal to determine anengine-power-related nominal preset signal as a function of the enginerotation speed; a speed control section which includes at least one of aspeed regulation stage which regulates vehicle traveling speed based onthe engine-power-related nominal preset signal, emitting anengine-power-related speed regulation control signal; and a speedlimiting stage which limits vehicle traveling speed based on theengine-power-related nominal preset signal, emitting anengine-power-related speed limiting control signal; and a power/torquecharacteristic stage at an output side of the speed control section, fortransforming an engine-power-related speed regulation or limitingcontrol signal output therefrom, to an engine-torque-related speedregulation or limiting control signal.
 2. The vehicle engine controldevice according to claim 1, wherein said control section comprises botha speed regulation stage and a speed limiting stage, and furthercomprising: a maximum selection stage which is supplied with theengine-torque-related nominal preset signal emitted by the torquecharacteristic stage and with the engine-torque-related speed regulationcontrol signal, and which passes on the greater of the two signals asthe output signal; and a minimum selection stage, which is supplied withthe output signal from the maximum selection stage and with theengine-torque-related speed limiting control signal, and which emits thegreater of the two signals as the engine torque control signal.
 3. Thevehicle engine control apparatus according to claim 2, furthercomprising: a switch which, when speed regulation and speed limiting areinactive, emits a signal that is representative of the operation of theengine operation preset control element and, when one of speedregulation and speed limiting is active, emits a signal, that representsthe effect of the speed regulation or the speed limiting, as a nominalvalue signal for electrical transmission control; and a transmissioncontrol characteristic stage, which uses an engine torque control signalto determine, as a function of the engine rotation speed, a signal for atransmission controller, which signal represents the effect the activespeed regulation and the speed limiting.
 4. The vehicle engine controlapparatus according to claim 1, wherein both the engine-power-relatednominal preset signal and the engine-power-related speed regulationcontrol signal or the speed limiting control signal represent signalsrelated to the accelerator pedal position level.
 5. The vehicle enginecontrol apparatus according to claim 1, wherein both theengine-power-related nominal preset signal and the engine-power-relatedspeed regulation control signal or the speed limiting control signalrepresent signals related to the throttle valve position level.
 6. Amethod for controlling engine operation in a vehicle having a driveroperated engine control element and a speed control section whichgenerates an engine power-related vehicle speed control signal as afunction of operation of said engine control element and of a presetdesired speed related value, said method comprising: generating anengine torque related nominal signal value as a function of operation ofsaid engine control element; determining an engine power related nominalsignal value as a function of said engine torque related nominal signalvalue; inputting said engine power related nominal signal value to saidspeed control section, said speed control section generating said enginepower related vehicle speed control signal as a function of said enginepower related nominal signal value and of a preset desired speed relatedvalue; determining an engine torque related speed control signal valueas a function of said engine power related vehicle speed control signal;and controlling operation of said engine based on said engine torquerelated speed control signal value.
 7. The method according to claim 6,wherein said engine power related vehicle speed control signal comprisesat least one of a speed limiting signal and a speed regulating signal.8. The method according to claim 6, wherein said first and seconddetermining steps are performed by means of stored characteristic data.